wip

Author: stephencelis

Sources/StructuredQueriesCore/AggregateFunctions.swift

@@ -84,7 +84,7 @@ extension QueryExpression where QueryValue: QueryBindable {
   /// - Returns: A maximum aggregate of this expression.
   public func max(
     filter: (some QueryExpression<Bool>)? = Bool?.none
-  ) -> some QueryExpression<Int?> {
+  ) -> some QueryExpression<QueryValue?> {
     AggregateFunction("max", self, filter: filter)
   }
 
@@ -99,7 +99,7 @@ extension QueryExpression where QueryValue: QueryBindable {
   /// - Returns: A minimum aggregate of this expression.
   public func min(
     filter: (some QueryExpression<Bool>)? = Bool?.none
-  ) -> some QueryExpression<Int?> {
+  ) -> some QueryExpression<QueryValue?> {
     AggregateFunction("min", self, filter: filter)
   }
 }

Sources/StructuredQueriesCore/Optional.swift

@@ -135,9 +135,41 @@ where Wrapped.TableColumns: PrimaryKeyedTableDefinition {
 }
 
 extension QueryExpression where QueryValue: _OptionalProtocol {
+  /// Creates and optionalizes a new expression from this one by applying an unwrapped version of
+  /// this expression to a given closure.
+  ///
+  /// ```swift
+  /// Reminder.where {
+  ///   $0.dueDate.map { $0 > Date() }
+  /// }
+  /// // SELECT … FROM "reminders"
+  /// // WHERE "reminders"."dueDate" > '2018-01-29 00:08:00.000'
+  /// ```
+  ///
+  /// - Parameter transform: A closure that takes an unwrapped version of this expression.
+  /// - Returns: The result of the transform function, optionalized.
   public func map<T>(
     _ transform: (SQLQueryExpression<QueryValue.Wrapped>) -> some QueryExpression<T>
   ) -> some QueryExpression<T?> {
     SQLQueryExpression(transform(SQLQueryExpression(queryFragment)).queryFragment)
   }
+
+  /// Creates a new optional expression from this one by applying an unwrapped version of this
+  /// expression to a given closure.
+  ///
+  /// ```swift
+  /// Reminder.select {
+  ///   $0.dueDate.flatMap { $0.max() }
+  /// }
+  /// // SELECT max("reminders"."dueDate") FROM "reminders"
+  /// // => [Date?]
+  /// ```
+  ///
+  /// - Parameter transform: A closure that takes an unwrapped version of this expression.
+  /// - Returns: The result of the transform function.
+  public func flatMap<T>(
+    _ transform: (SQLQueryExpression<QueryValue.Wrapped>) -> some QueryExpression<T?>
+  ) -> some QueryExpression<T?> {
+    SQLQueryExpression(transform(SQLQueryExpression(queryFragment)).queryFragment)
+  }
 }